Taxonomic revision of white-flowered Isoglossa Oerst. (Acanthaceae) in southern Africa

The taxonomy of the white-flowered species of Isoglossa Oerst. in southern Africa is reviewed. Morphology and indumentum of bracts and calyces, micromorphology of pollen and seeds, flowering times and distribution are documented. Several names are subsumed: Isoglossa densa N.E.Br. and Isoglossa sylvatica C.B.Clarke under Isoglossa ciliata (Nees) Lindau; Isoglossa grantii C.B.Clarke and Rhytiglossa glandulosa Hochst. under Isoglossa woodii C.B.Clarke; Isoglossa bolusii C.B.Clarke under Isoglossa macowanii C.B.Clarke; and Isoglossa eckloniana (Nees) Lindau under Isoglossa origanoides (Nees) Lindau. Two new species, Isoglossa pondoensis K. Balkwill and Isoglossa gracilenta K. Balkwill, are described.